We move to the big break in the hunt for the masked executioner of American hostage James Foley. Officials are close to identifying who this jihadist is. Now the race son to find him before he strikes again. ABC's chief white house correspondent Jon Karl has the latest from mar T Martha's vineyard. Reporter: He's known as jihad John. Now one of the most wanted men in the world. U.s. Officials believe we may soon know who he really is. ABC news has learned U.S. And british intelligence is closing in on the identity of the masked executioner who oke with a british accent. His own words are proving critical. We're confident he'll be identified, a senior U.S. Official tells ABC, and identified soon. You have plotted against us and gone far out of your way to find reasons to interfere in our affairs. Reporter: They're working to match the executioner's voice with a database of british nationals suspected of terrorist ties. They're also attempting to match the voice with communications now being monitored. They may be able to place it in a particular part of England. Reporter: In addition to Foley and Steven sotloff, U.S. Officials believe they're holding two other Americans. U.s. Law enforcement son high alert for isis-backed or inspired attacks on U.S. Targets at home and abroad. An FBI bulletin says we're unaware of any specific credible threat but warns Isis has demonstrated the capability to attempt attacks on U.S. Targets overseas with little to no warning. Reporter: The president returns to Washington late tonight. Top of his agenda is what to do next. And with whether it's time to expand U.S. Air strikes to include targets in Syria as well as Iraq. Paula? Dan? So many big decisions looming for the president. Let's bring in George stephanopoulos, chief anchor and host of "This week." Let's start with what they can do if they figure out who the executioner is. Do they take him out with a drone strike or put him on trial? I think they most certainly will try to take him out. That's been the modus operandi of the United States for this kind of thing. The president now considering whether to expand the air strikes from Iraq to Syria, where Isis has many bases. Not long ago this president described Isis as a JV team. How did it go from that to now actively considering expanding the supposedly limited air strikes into another country? I think the entire administration was taken by surprise with how dramatically Isis gained territory and red over the last six months. You're right. The president spoke of this as a JV team earlier this year. Now chuck Hagel is saying this is an imminent threat to the United States. One of our guest this is morning, general John Allen is calling this a clear and present danger to the United States. He's calling for da mattic escalation in the campaign against Isis. A lot of debate about whether they can or will attack us here on the homeland. George will be talking about the threat from Isis with congressman Michael Mccaul. Later this morning on "This week." George, thank you. Now to some big weather problems that could affect the U.S. Later this week.

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